1. Field of Invention
Embodiments of the invention relate generally to semiconductor devices and, more particularly, to methods of fabrication of such semiconductor devices having buried digitlines and wordlines.
2. Description of Related Art
Many types of electronic devices include data cells with a single transistor. Typically, the transistor controls whether a stimulus (e.g., a current or voltage) is applied to, or by, a data element (e.g., a memory element, an imaging element, or other device configured to output data, such as various kinds of sensors). Often a large number of data elements are disposed in an array, and the transistor allows individual data elements in the array to be selected. For example, certain types of dynamic random access memory (DRAM) cells include both a capacitor, which functions as a data element, and a single transistor, which functions as an access device, connected to the capacitor. The capacitor usually stores data by storing a charge that is representative of data (e.g., a 0 or a 1 in a single-bit device, or a 00, 01, 10, or 11 in a two-bit device), and the transistor typically controls access to the capacitor by controlling the flow of current to and from the capacitor, allowing current to flow during reading and writing and preventing current from flowing when retaining data.
Often the data elements are arranged in an array, e.g., generally in rows and columns. Data cells within the array are accessed, e.g., written to or read from, through circuitry near the periphery of the array. For instance, sense amplifiers or other sensing circuitry are often positioned adjacent arrays of data cells for reading data. Similarly, address decoders, e.g., row and column address decoders, are often disposed adjacent the array for addressing particular data cells or groups of data cells.
As the footprints of such devices become smaller, the components of the device may become smaller and/or denser for a given storage capacity. Additionally, some structures may be more vertical (i.e., less planar with respect to the substrate) to reduce footprint size. In such devices, construction of the data elements and the support structures (e.g., digitlines, wordlines, etc.) may present challenges and may limit scaling such devices to smaller footprints and higher densities.